The present invention relates generally to fastener driving tools, and more particularly to an improved fastener driving tool configured to drive a threaded fastener using both linear and rotational motion.
Threaded screw fasteners are well known in the art and are widely used for numerous fastening applications. In one such application, threaded screw fasteners are used to fasten a surface material, such as exterior gypsum sheathing or interior drywall, to a substrate material, such as steel or wood framing elements (studs).
Threaded screw fasteners may be driven using any of a variety of prior art fastener driving tools, such as manual screwdrivers and powered driving tools, such as screw guns. Powered driving tools, which are commonly used in the construction industry, may be powered by various means, such as electrically, pneumatically, by combustion or by combinations of the foregoing.
In high production settings, threaded screw fasteners may be stored in a carrier strip which feeds the fasteners to the powered driving tool in a continuous, rapid fashion. Such carrier strips generally comprise a plurality of evenly spaced apertures through which the screws extend transversely with the fastener heads resting near or against the carrier strip. In this manner, the fasteners may be quickly fed to the powered driving tool which engages each fastener in the carrier strip and, by linear and/or rotational movement, detaches the fastener from the strip and drives it into the material.
One challenge faced by installers is that, upon driving the fastener, the generally large diameter head of the fastener should be flush with, but not pierce the face paper outer layer of the surface material. If the fastener passes through the face paper, the board is structurally weakened at that point, and may require additional finishing.
Another challenge faced by installers is that when the surface material is applied to substrate material, the fastener typically easily passes through the relatively soft surface material, but in some cases has difficulty penetrating the harder substrate material. Therefore, when driving fasteners into a relatively hard substrate materials, additional force is required to cause the fastener to penetrate the substrate material and to engage the threads of the fastener with the substrate material.
Even when special cutting- or drill tip-type fasteners are used, the substrate material sometimes may be pushed away from the rear surface of the surface material. Thus, in some cases, the fastener may pierce the substrate material on an angle relative to the surface material. Subsequent tightening of the fastener therefore may fail to form a tight connection between the surface material and the substrate material at that point.
Additionally, because the process of rotationally driving a threaded screw fastener for the entire length of the fastener shank adds time to the fastener driving process, it would be advantageous to reduce to number of rotations required to drive the fastener. For, in a high production setting, even a small amount of time saved when each fastener is driven can add up to a significant time savings over the course of hundreds or thousands of fasteners.
The prior art has developed tools designed to address some of these challenges. Powered driving tools configured to engage a threaded screw fastener stored in a carrier strip, separate the individual fastener from the carrier strip by linear motion (that is, motion in the direction of the longitudinal axis of the fastener) and drive the fastener into a material using rotational motion are known in the art.
For example, U.S. Pat. No. 5,862,724 to Arata et al. discloses a pneumatic fastener driving tool having both linear and rotational driving functions. In the disclosed tool, a driver blade is disposed within a cylinder and is driven both linearly (by a piston) and rotatably (by an air motor). The air motor (and its associated planetary reduction gear system) travels with the driver bit as it reciprocates in the cylinder.
One drawback of the disclosed tool, however, is that it has insufficient power to drive a fastener into harder substrate materials, such as a light gauge steel studs, which are commonly used in the construction industry.
Still another drawback of the disclosed tool is the relatively high recoil generated by the tool as a result of the linear, reciprocating movement of not just the driver blade, but also the air motor, the planetary reduction gear system and the multiple pistons, within the tool. The significant recoil generated by this prior art tool can disengage the fastener-driving bit from the fastener head. In such cases, a separate tool such as a power screwdriver is needed to complete fastener installation.
Thus, there is a need for a powered fastener driving tool which addresses the above-identified drawbacks of prior art fastener driving tools. Desirably, such a tool is configured to drive a fastener using both linear and rotational movement, effectively acting both as a nail gun and as a screw gun. More desirably, such a tool has sufficient linear force to drive a fastener into a relatively hard substrate, such as a steel stud. More desirably still, such a tool comprises an air motor assembly and a gear reducer assembly that do not travel linearly within the tool in order to reduce recoil generated during the driving process. Even more desirably, such a tool uses a compound planetary gear reducer assembly to advantageously reduce the overall length of the tool. Most desirably, such a tool is pneumatically powered and may be used with numerous prior art air compressors.